With increasing development of science and technology, a variety of electronic appliances are designed in views of convenience and user-friendliness. For helping the user well operate the electronic appliances, the electronic appliances are gradually developed in views of humanization. The common electronic appliances include for example notebook computers, personal digital assistants (PDAs), mobile phones, satellite navigation devices, digital cameras, or the like. Recently, the storage capacity and the processor's computing performance for these electronic appliances are largely enhanced, and thus the functions thereof become more powerful and complicated. For efficiently operating an electronic appliance, a touchpad is used as an input device of the electronic appliance for controlling operations of the electronic appliance.
FIG. 1 is a schematic diagram illustrating a notebook computer and a touch device thereof according to the prior art. As shown in FIG. 1, the touch device 1 is installed on the base 21 of the notebook computer 2. The touch device 1 includes a touchpad 11, a left button 12 and a right button 13. For operating the notebook computer 2, the cursor 23 shown on a display screen 22 is moved by touching and moving a user's finger on the touchpad 11. The uses of the left button 12 and the right button 13 may implement some functions in replace of the conventional computer mouse. In other words, the user may operate the notebook computer 2 through the touch device 1 without the need of additionally carrying or installing the notebook mouse.
Conventionally, the touchpad 11 is operated to control movement of a cursor 23 shown on the display screen 22 in a relative coordinate mode. The way of controlling cursor movement in the relative coordinate mode is the same as the way for controlling the cursor with a mouse. That is, regardless of the actual position of the user's finger on the touchpad 11, the distance and the direction of the cursor are determined according to the direction and displacement between the final position and the initial position of the user's finger on the touchpad 11. Since the area of the touchpad 11 is much smaller than that of the display screen 22, if the user wants to move the cursor 23 from an end of the display screen 22 to another end of the display screen 22, the user has to slip the finger on the small area of the touchpad 11 repeatedly to accumulate enough amount of displacement. In other words, the way of controlling cursor movement in the relative coordinate mode is troublesome.
For solving the above drawbacks, the touchpad 11 is operated in an absolute coordinate mode to control the cursor movement on the display screen 22. In the absolute coordinate mode, any position on the display screen 22 corresponds to a specified position on the touchpad 11. The way of controlling cursor movement in the absolute coordinate mode is similar to the way for controlling the existing touch screen. For example, the user may move the cursor 23 to the middle of the display screen 22 by simply placing the user's finger on the middle of the touchpad 11. As known, the way of operating the touchpad 11 in the absolute coordinate mode fails to compete with the way of operating the touch screen because the area of the touchpad 11 is much smaller than that of the display screen. If the user wants to point and control a small object on the display screen by operating the touchpad 11, it is difficult to precisely move the cursor to the desired position. Although the increased area of the touchpad 11 may facilitate precisely positioning the cursor, the overall volume of the notebook computer will be increased and detrimental to carry.
For solving these drawbacks, several touch devices were disclosed for allowing the user to selectively operate the touchpad in the absolute coordinate mode or the relative coordinate mode according to the practical requirements. These touch devices were disclosed in for example Taiwanese Utility Patent No. 241746, Taiwanese Utility Patent No. 470193 and Chinese Patent Publication No. 1940837. However, the touch devices disclosed in these literatures need an additional hardware component or an additional mode-switching key for switching the operating mode of the touchpad between the absolute coordinate mode and the relative coordinate mode. In addition, during the touch process, if the user wants to switch the coordinate mode, the user needs to press the additional hardware component or key. In other words, the touching operation and the coordinate mode switching operation fail to be simultaneously done.